I have 6 Hibiscus plants that were at a new house when i bought it. I do not know what kind they are. Last year they all sprouted and grew and had huge beautiful flowers all summer.some of the stems are almost 1inch diameter. In the fall I cut all the stems back. (thats what the previous owner told me to do) they are planted in 3 different places in the yard. They should beginning to show signs of re-sprouting but only one of the plants are growing, and it is a different kind than the others.5 of the plants have a hole in the middle of the stem? I am in NW arkansas. Did they get some kind of bug and die?